Effects of grazing two mixtures of forage species on ewes milk production under climate change condition

Abstract

In Sicilian forage systems, it is still necessary to identify species that allow to maintain over time meadows for grazing. Native grassland species such as Sulla (Sulla coronaria L.) represent a resource with well-known potential in Mediterranean environments. The intercropping combination of sulla with other self-seeding species (e.g. chicory or other cosmopolite species such as clover) would represent a useful strategy to implement grazing resources in Sicilian forage systems. This research aimed to evaluate the effects of continuous grazing of different intercropping forage legume species on live weight (LW), BCS and milk yield and composition in ewes. The forage species were (i) mixture of Sulla, Medicago polymorpha L., and Cichorium intybus L. (SMC); (ii) mixture of Medicago truncatula L., Medicago polymorpha L., and Medicago scutellata (MMM). Twenty lactating ewes of Valle del Belice breed were homogeneously divided into four groups of five ewes on the basis of lactation phase, milk yield, BCS and LW; each group was assigned to one of four grazing sectors of 1500 m2, consisting of two replicates of SMC and MMM. LW and BCS of ewes were recorded at start and end of trial. Ewes’ milk yield were recorded daily, while individual milk were sampled 3 times, every 8 days, and analysed for its components and clotting ability. During the trial forages were sampled to determine chemical composition. During the experiment, lasting 25 days, there was a gradual decrease in milk yield which resulted less pronounced for SMC group than for the group grazing on the other forage mixture. Therefore, the ewes fed on SMC mixture showed a significantly higher milk yield in comparison with the ewes grazing on the mixture MMM (1334 vs 1153 g/d; p < 0.05). Furthermore, the milk produced by SMC ewes was characterized by higher protein (5.17 vs 4.85 %, p < 0.001) and casein percentages (4.02 vs 3.73 %, p < 0.001), lower urea content (37.70 vs 45.38 mg/dl p < 0.001) and better clotting parameters measured with Formagraph (a30 and a2r, p < 0.001). Finally, at the end of grazing period, ewes of SMC group showed a less reduction in LW compared to MMM ewes (−2.05 vs -3.55 kg, respectively), although the difference did not reach a significant level. The results obtained seem to highlight the promising role of the SMC intercrop, leading to a potential quantitative-qualitative improvement of pasture resources and productive performance of grazing ewes in a semi-arid Mediterranean environment.